Dielectric materials such as silicon oxide (SiO.sub.x wherein 1&lt;x&lt;2) are widely used in the manufacture of semiconductor devices. These materials find use not only as final passivation coatings for completed devices but also as intermediate insulating layers for multi-layer devices. Thermally grown oxides, such as silicon oxide, are typically employed as dielectric films, e.g. a gate dielectric, in semiconductor devices such an EAROM (electrically alterable read only memory), a MOSFET (metal-oxide-semiconductor field effect transistor), capacitors and the like. Thermal oxidation methods, by which the best silicon oxide films are produced, are usually carried out by placing silicon in an oxygen ambient at temperatures between 800.degree. and 1200.degree. C. In many situations these temperatures are too high for the substrate. For instance, in applications where the dielectric film to be formed is part of a semiconductor device being fabricated over a glass substrate, lower process temperatures are required. Specifically, in the area of liquid crystal displays, thin film transistors are fabricated over glass substrates having a softening point of about 650.degree. C. Therefore, to thermally grow an oxide onto silicon over glass, the temperature of the substrate in the oxygen ambient is kept at about 600.degree. C. which requires about 120 hours to grow 60-70 nanometers (nm) of silicon oxide.
Silicon oxide (SiO.sub.x), aluminum oxide, and silicon nitride can be deposited at temperatures below 600.degree. C. by glow discharge and other chemical vapor deposition (CVD) techniques, in a fraction of the time required for thermal growth, e.g. a few hours or less. However, the dielectric quality of the deposited film is poor compared to the thermally grown material. Specifically, the transistor turn on voltage for deposited silicon dioxide films is typically unstable. It is believed that charge traps within the film and/or at the silicon-dielectric interface cause the film to accumulate a charge upon the initial applications of voltage. Subsequent applications of voltage are characterized by a shift in the tun on, or threshold, voltage of 5 to 10 volts or more, compared to little or no shift in the threshold voltage for thermally grown oxide.
Further, in applications requiring a dielectric over hydrogenated amorphous silicon, it is desirable to keep processing temperatures below about 400.degree. C. This is because the semiconductive properties of amorphous silicon change at temperatures above 400.degree. C., probably due to a loss of hydrogen from the film above that point.
It would be desirable therefore to have a method of producing a dielectric film at a temperature below 600.degree. C. and preferably below 400.degree. C. wherein the rate of film formation is substantially increased over thermally grown films in that temperature range without a substantial sacrifice in dielectric stability.